This invention relates to range finders, specifically to a range finder that relies on the reduction in the size of an object""s image as distance increases, as viewed through an opening in the range finder, to determine the object""s distance from the user where the object""s width, length, height or other visible linear dimension is known or can be estimated.
There has been a long-standing need for xe2x80x9crange finders,xe2x80x9d ie., devices that allow the user to gauge his or her distance from an object without physically measuring the distance. Although various devices have been utilized for this purpose, two categories of range finder are relevant here: (1) xe2x80x9cimage-basedxe2x80x9d range finders that use the decrease in size of an object""s image as distance increases to determine what that distance is; and (2) devices that can bounce a signal or beam off a target object, such as sonar, radar and laser range finders. The instant invention is an image-based range finder that improves upon the prior image-based art and, in addition, in some instances, complements or substitutes for signal reflection range finders.
It has long been known that the perceived size of an object""s image decreases with distance. This phenomenon has been the basis for simple range finding devices, which have used, for instance, a ruler to measure the size of the object""s image. If the user knew both one linear dimension of the object and, via the ruler, the size of the image of that dimension, he could determine his distance from the object by using the well-established formula d=xy/z, where d is the object-to-eye distance, x is the known dimension of the object, y is the eye-to-device distance and z is the size of the image as measured by the ruler. Of course, if d is known, z can like wise be predicted (z=xy/d). As further discussed below, devices based on this concept have mainly taken three forms: reference line devices, stadia-line devices and window-based devices.
Most common in this category of range finders are devices that employ a reference line comprising a system of measurement. Essentially a ruler drawn across the reticle of a scope, this device permits a comparison between the image size and previously determined distance information. Thus, in periscopes on submarines, distance to a surface ship has been roughly calculated based on the measurement provided by an engraved reference line on the reticle and compared to separately compiled information on the dimensions of various ships. This device provided a numeric measurement of the apparent size of the measured object which would then be compared to previously determined distance information calculated through the distance formula discussed above. Generally, this involved an additional step separate from the device itself These devices can determine distances from differently sized objects, but they pose difficulties in object alignment (i.e. having to superimpose a thin line over the image while simultaneously measuring the image size), and they require the user to access separately compiled information.
Stadia-line range finders are a conceptually and practically distinct category utilizing similar distance determination principles. In these devices, a series of lines with accompanying numerals denoting distance are expressed on the reticle of a telescope or viewfinder. Each line is a different length and corresponds to the size of an image of an object of known dimension at a particular distance. The placement of lines and their lengths are also determined by the formula z=xy/d. Consequently, the plurality of lines, when centered on the reticle, have generally formed a curvilinear shape. In operation, the user superimposes the appropriate line over the object image in order to determine distance. This approach allows for the user to view the object image and access distance information at the same time, but it is less flexible than reference line devices because the stadia lines can only determine distance to one dimension of one item. Like reference line devices, this device partially obscures the target object.
A conceptually and practically distinct category utilizing similar distance determination principles is the xe2x80x9cwindow-basedxe2x80x9d range finder. Such devices enclose the object image at a particular position on an opening and correlate the image size to previously determined distance markings imprinted adjacent to the opening. The advantages of this art over reference-line devices are that the opening makes target alignment much easier, and the distance information imprinted on the device itself allows for a quicker determination of distance in that this information does not need to be separately accessed. It is superior to stadia-line art in that the object image is more easily framed and the user""s view of the object is not obscured. However, as discussed below, window-based range finders have had several serious limitations, and their use has been limited.
Other range finders in this general area are a range finder having a notch sized to accommodate the image of one object at one distance (Williams, U.S. Pat. No. 3,977,086); a range finder that interposes one or more two-dimensional outlines of the entire object image (e.g., a full representation of a deer) in a viewer or scope (Gregory, U.S. Pat. No. 4,787, 739); a range finder that discloses a vertically expressed reference line with unevenly spaced calibration lines (Murdoch U.S. Pat. No. 4,263,719); and a range finder that causes a reference line in a viewer to vary in length, making it easier to measure image size. (Landon, U.S. Pat. No. 3,999,853).
An additional category of distance determination art is found in devices that can bounce a signal or beam off a target object back to a receptor (e.g., radar, sonar and laser devices). These signal reflection range finders, while not directly related to the instant invention, offer an alternative prior art category of distance determination devices.
Image-based range finders have to date been quite limited in their effective uses.
To our knowledge, image-based range finders have thus far not been used to determine short-range distances (ie., less than 60 feet). This is not surprising because making a useful device is more complicated for short-range distance determination. Even though the standard formula d=xy/z, which is applicable to distance determination and has been used in the prior art, can generally predict the size of the image at a short distance, it is often not the sole determinant. At short ranges, additional factors which do not exist (or are practically irrelevant) at longer ranges become more important. Thus, depending on the circumstances, the device may have to account for the height of the user, changes in the distance at which the device is held, and differences in the way the eye views objects at very short range. Although such adjustments are not always necessary, they would likely have presented significant difficulties. A device that has the flexibility to adjust for such factors where necessary and to provide for distance determination at relatively short distances would be a substantial improvement over the prior art, which is tied to the standard formula.
In addition, we understand that image-based range finders have thus far not been used to estimate distances to relatively small objects (i.e., objects with a linear dimension of less than 1.5 feet), such as a golf hole on the golf green. Useful applications for such a device would have been thought limited given that (1) absent a magnifying element, only short ranges can be determined, and (2) the less distance involved, the more likely the need for precision. (A margin of error of 25 yards might well be acceptable in a range finder for use in a periscope range finder but not, for example, in a device for the putting green). Moreover, because the object is small, distance measurements quickly become xe2x80x9clong-rangexe2x80x9d in that the object appears very small and the rate of decline in image size slows such that a relatively small change in image size (z) could indicate a substantial change in distance (d). In these conditions, the prior art, thought applicable in theory, may well have been an impractical option because (1) a user of a reference-line device would have great difficulty pin-pointing image size with sufficient, precision to yield a reasonably precise result; and (2) the maker of a stadia-line or window-based device, as discussed more fully, below, would need to form either a very long opening to accommodate the window or lines or make the distance-indicating lines very close together. Thus assuming anyone had thought to apply the prior art to short-range applications, it would not have been obvious that a practically useful device could be made.
Further, image-based range finders have not been used to determine distances from the user or an object on the ground at the user""s feet, such as a golf ball, to another nearby object on the ground, such as a golf hole. There may be many reasons for this, including those set forth herein, but one is specific to this situation. The application of the z=xy/d formula alone will not render an accurate result in this context. In order to create a device for determining the distance from an object adjacent to the user""s feet to another object on the ground, as determined though the user""s eyes, or the distance from the user""s feet to a distant object on the ground, the device must be adjusted in accordance with the formula a2=b2+c2, where a is the distance from the eye to the desired object on the ground, b is the distance from the user""s eye to the object at the user""s feet (or the ground) and c is the distance from the desired object to the object at the user""s feet (or the user""s feet). While use of the formula a2=b2+c2 may be necessary in various applications of the formula z=xy/d, it is particularly important in situations such as this where there is a significant variation in the levels of the eye and the desired object that by definition cannot be assumed away. Thus, any device based solely on the z=xy/d formula could be significantly inaccurate in these circumstances.
In addition, the application of the standard formula (z=xy/d) to the prior art has generally required that there be an assumed or constant eye-to-device distance. The prior art has assumed a certain eye-to-device distance or required a string or other non-flexible appendage to hold the device at a constant eye-to-device distance. In many applications, such assumptions or appendages are appropriate methods to implement the traditional formula. However, their flexibility has been limited. It has been difficult to adjust where necessary or useful to varied arm lengths or other potential variations in the user""s device positioning. A device that can, where appropriate or useful, adapt to such variations would be an improvement.
While the window-based range finder is perhaps the most user-friendly of the image-based range finders, it has, until now, suffered from additional significant limitations. Typically, the shape of the windows in these devices has been required to be curvilinear. In many instances, the distance markings have been required to be uniformly spaced. The requirement to apply such a curvilinear shape with uniform distance markings substantially limits a manufacturer""s ability to make a commercially successful device. In essence, the established distance formula (z=xy/d) as applied in such devices determined both the shape of the device and the means to measure the distance. In addition to a general lack of flexibility in device design, such requirements would limit the range of distances a device could determine. For example, a window intended to estimate long-range distances (i.e., distances at which the target object appears to be very small) must necessarily be quite long because the slope of the curvilinear line begins to flatten as the rate of decline in image size slows. This problem would be even more pronounced when one sought to make a device for determining a large range of distances (e.g., long-range, mid-range and short-range). Once again, such a window would be much too long for practical use and/or would have markings that are much too close together to easily read. These shape and markings requirements would also limit the device to distance determination for one dimension of one item. In this regard, the shape of the window is specific to the size of the item to be measured, ie., other items of different sizes could not be accommodated on the same device. Similarly, the fact that the window must be a certain size and shape limits the options of the manufacturer to, for example, incorporate the range finder into another device. A window-based range finder that does not require a curvilinear shape and that does not depend on equally spaced lines would unlock a previously unexplored potential of such devices.
The limitations of the window-based range finder prior art can be seen in two representative devices, both relating specifically to determining mid-range distances from the flag stick or xe2x80x9cpinxe2x80x9d on a golf course (New: U.S. Pat. No. 3,409,987; Liao: U.S. Pat. No. 5,211,395).
The New patent discloses an invention solely for determining the mid-range distance (from 80 yards to 200 yards) from a golf pin of a standard height of 7.5 feet. The device consists of a card member with an opening having (1) a bottom horizontal line with uniform linear graduations imprinted on the opaque surface adjacent to the opening; and (2) a top line that is curvilinear. The shape of the opening is absolutely determined by the z=xy/d formula. The graduated lines are evenly spaced along the bottom line. In practice, the user would hold the device at a length of 20 to 25 inches from the eye, align the flagstick in the opening, and read the corresponding distance based upon the markings on the bottom line. If the pin is not 7.5 feet in height, the device can be adjusted as follows: the user must stand 20 yards from the pin, turn the device on its side, line up the image of the pin by moving the device closer or farther away from the eye until it fits the opening, and thereafter hold the device at exactly that distance from the eye through memory, a string attached to the device, or marks on a golf club.
The Liao patent discloses a highly similar device incorporated into a putting green repair tool. Here, a curvilinear V-shape created by the two prongs of the putting green repair tool forms an opening similar to that disclosed in the New patent. Uniformly spaced lines along the prongs indicate the proper distance (60 to 200 yards) and golf club to be selected. The shape of the opening is determined by application of the z=xy/d formula. The opening is formed through the convergence of the two curvilinear edges of the prongs of the tool. An inelastic string is used to ensure a consistent eye-to-device distance. The Liao device does not appear to be adjustable.
The New and Liao patents by their terms are limited to a specific measurement of the mid-range distance (60 to 200 yards) to the pin. Neither makes any claim or discloses any object or application relating to determining the distance from any other object (including on the golf course); determining short-range or long-range distances; determining distances between objects on the ground; using a non-curvilinear opening of any other shape; using a series of openings, using distance markings that are not evenly spaced; adjusting the range finder (except as described above) to accommodate differently-sized objects or different distances between the eye and the device; or incorporating the invention into an adjustable electronic range finder. As discussed above, this is likely to be due to the inherent limitations of the prior art.
Almost all range finders other than reference line devices (which have their own limitations), have been designed to determine distances to only one object of a particular dimension, such as a golf flag stick. For example, the length of each line in a stadia-line device, and the shape of the window in a window-based device, are determined by the formula as described above (z=xy/d) and have not been altered to accommodate multiple objects of different sizes. For an example of how difficult it has been to create even minimal adjustability in such devices see New U.S. Pat. No. 3,409,987. Gregory U.S. Pat. No. 4,787,739 discloses an electronic device that allows the user to electronically change the predetermined outline of an object expressed on a liquid crystal display reticle in a scope such that, by pressing a button, a differently sized outline of a deer or other object will appear in the reticle. It is unclear whether this is a significant improvement over the prior art since the user must select one outlined image, determine if it fits the object image, pick again if not, and repeat the process until the outline image corresponds with the object image. In most instances, a device that requires a trial-and-error process, electronically enhanced or not, is not adaptable to the usual desire of the user for a quick determination of distance. A window-based device that could determine distance to more than one object would be quite useful.
The advent of devices that can bounce a signal or beam off a target object (e.g., radar, sonar and lasers) marked a substantial improvement. Today, signal reflection range finders are exceedingly fast, accurate and applicable to many distance determination problems. However, such devices have several limitations, including cost of manufacture, size and weight. Signal reflection range finders are also limited by the conditions under which they can be used, often warning that their effectiveness is limited in bright, foggy, misty, rainy or snowy conditions, or that their effective range varies with the color, shape or reflectivity of the target object. In addition, the use of high tech components increases the risk of component damage or failure. In many cases, such devices also require ongoing efforts to maintain the power source. A device which could solve many of the same distance determination problems addressed by signal reflection range finders without many of their limitations would also be a significant improvement.
The various image-based range finders have historically been quite limited in their effective uses for many reasons, including (1) the need to rely on lines or openings that interfere with the user""s view of the object and/or that must be a particular size or shape, (2) the difficulty in making a device that is adjustable to differently sized objects or different eye-to-device distances, (3) the difficulty in using the devices to determine relatively long distances, (4) the difficulty in determining distance to relatively small objects, and (5) the difficulty in using such devices to determine relatively short distances or to determine distances between objects on the ground.
Today numerous distance determination problems remain unsolvedxe2x80x94and would not be feasibly or easily solved by the prior art. For example, in the six centuries since the invention of golf, no device, laser-based or otherwise, has been developed that allows the user to determine distance on and around the putting green to the golf hole, knowledge of which is an important element of the putting game. No simple, relatively low-cost-of-manufacture device has been developed to allow a target shooter or other person to determine distance to the target without physically measuring the distance. No simple, relatively low-cost device allows a sports coach, gym teacher or other person, in setting up the boundaries and other parameters of athletic games, to determine distance to buoys, bases, goals, chalk marks or the like with reasonable accuracy. A soldier in the field has no lightweight, relatively low-cost distance determining option to replace, complement, test or xe2x80x9cback upxe2x80x9d a signal reflection range finder. No device exists for these or other purposes allowing for simple, adjustable range finding without the use of a bounce-back signal or beam. And no electronic window-based device provides a fully adjustable range finder capable of determining distance from a wide variety of objects of different sizes through one opening. As set forth below, our invention solves a far broader range of distance determination problems, such as the above examples, xe2x80x94and/or solves them at a much lower cost and reduced complexityxe2x80x94than any prior art.
The instant invention is an image-based range finder. In each of its embodiments, the invention relates to, and relies on, the fact that the image of an object appears to decrease in size as distance from the object increases. The invention expands dramatically the types of image-based range finders that may be constructed by eliminating the need to depend on curvilinear shapes on equally spaced lines and markings. The invention further incorporates a new use of image-based range finders by determining relatively short ranges to relatively small objects, and determining distances from an object on the ground to another object on the ground at the user""s feet or to the user.
In its window-based embodiments, the invention can take the shape of a card, viewer, scope or any other structure (which may include a focusing, magnifying, or image-reducing element) containing or including an opening, aperture, prongs, window or series of windows allowing the user to view a distant object through the opening in such a way that the image of the object appears to touch, without being obscured by, at least two sides of the opening at a specific position on the opening for each particular distance from the object. Marks, lines, numerals, tables, stored data and/or other expressions of predetermined distance information are indicated on or incorporated into the invention such that the user can relate the size of the object image to previously determined distances. The shape of the opening is variable, i.e., its shape does not depend, except in the most general way, on the z=xy/d formula described above. However, this formula is taken into account in the determination and expression of the distance information on or in the invention.
When the invention is to be used to estimate relatively close distances from an object on the ground at the user""s feet, such a golf ball, or the user himself, and another object on the ground, such as the golf hole, an additional adjustment to the opening or distance information is needed to account for the height of the user, or a chosen average height. The z=xy/d formula as described above is adjusted in accordance with the additional formula a2=b2+c2 (where a is the distance from the eye to the desired object, b is the height of the eye, and c is the distance from the object at the user""s feet or the user""s feet to the desired object) to provide for the correct eye to desired object distance. While this formula could be theoretically considered in all distance determination instances, its practical relevance increases in circumstances such as these. Through use of this additional formula, the distance information and distance markings can be accurately determined. In some cases, the device can be implemented with averaged data. In such circumstances, the more accurate information provided based upon the application of the additional formula above would allow for more accurate average information for inclusion in the device as well. In some circumstances, additional trial and error observations may prove useful to take into account other variables such as the method of holding the device or vision adjustments at very close distances.
In this specification, various window-based embodiments are disclosed. In practice, the user holds the device at a specified approximate distance from the eye (which may include holding the device against the eye), aligns the image of an object of known or estimated width, height or other linear dimension so that the image appears to just xe2x80x9ctouchxe2x80x9d two sides of the opening, and the user then determines the approximate distance to the object by relating the position of the image within the opening to recorded distance information, such as lines, marks, numerals, tables or other stored information. While the various embodiments focus on the window-based range finder, it should be understood that lines drawn across a transparent viewing portion which are drawn to define the included area of a window would be included in the disclosed embodiments as well. For instance, this would include instances in which stadia-lines are drawn to illustrate the distance between the long sides of an isosceles triangle shaped range finder window at various points.
By creating the conditions for variable shapes and distance markings, the invention also makes it easier to make one window-based range finder that can determine distances from a broad variety of differently sized objects, where at least one known or estimated linear dimension of each desired object is available. Thus, in some embodiments a system of measurement is expressed on or adjacent to the edge of the opening such that the user can determine the exact position on the opening where an object""s image appears to touch, without being obscured by, at least two sides of the opening. Recorded in, on or separately from the range finder is information correlating all relevant distances, object dimensions, and positions on the opening. In operation, and by way of example, the user (1) aligns the target object (e.g., a 10xe2x80x2 long truck) in the opening; (2) notes, using the system of measurement, the exact position on the opening where the relevant dimension appears to just touch two sides of the opening (e.g., 2xe2x80x3 from the vertex of a triangular opening); and (3) accesses the relevant distance information calculated through use of the z=xy/d formula, adjusted as necessary by the formula a2=b2 +C2. In this example, the device would show that a 10xe2x80x2 long truck is a particular distance away from the user when its image is cabined by two sides of the opening at a by position that is two inches from the opening""s vertex. Note that, unlike a reference line device, it is not the image that is being measured, but the image""s position on the opening. We do not believe that any prior art is based on correlating image position in an opening to recorded distance information. Note also that, while the opening could be formed through the convergence of curvilinear lines, there is no particular reason to do this, since the narrowing of the opening is not determined by plotting points in conformity with a formula.
Accordingly, it is an object of the present invention to provide a range finder that:
(1) is relatively simple, light-weight, portable, low-cost, and rugged, particularly as compared to signal reflection range finders;
(2) can be made to provide a means by which a person can determine distance to a visible object if the height, width or other linear dimension is known;
(3) determines distance by viewing an object through a portion, an opening, aperture, prongs, opening or series of openings that does not have to be a particular shape;
(4) relates the size of an object""s image at a particular distance to lines, marks and/or numerals that need not be evenly spaced;
(5) can be made to determine the distance to any object visible to the eye with or without the aid of a magnifying, focusing, image-reducing or other vision-enhancing element;
(6) can be made to determine relatively short and long distances;
(7) can be made to be adjustable to different object sizes and different eye-to-device distances, where appropriate, without changing the shape of the opening;
(8) can form a far more adjustable window-based range finder by linking individual range finders which can accommodate different object dimensions or different distance ranges;
(9) can accommodate a wider range of distances than a typical window-based or stadia-line range finder;
(10) can be made to allow the user to determine the distance from a point on the ground (such as a golf ball) to another point on the ground (such as a golf hole);
(11) can be made to allow a target shooter, archer or other person to more easily position him or herself from a target;
(12) can be made to provide a hunter, soldier or any other person with a distance determination problem with a range finder that can replace, complement, back up or test existing signal reflection range finders;
(13) uses less energy than laser-based range finders, i.e., requires no separate power source or a much smaller power source;
(14) can be used in any lighting or atmospheric conditions that allow the user to see the object; and
(15) can be used regardless of the color or shape of the object.